Recent experiments with nonprecious-metal HOR electrocatalysts needed to overcome two major challenges, the researchers wrote: low intrinsic activity from too strong a hydrogen binding energy, and poor durability due to rapid passivation from metal oxide formation. To overcome these challenges, the researchers designed a nickel-based electrocatalyst with a 2 nanometer shell made of nitrogen-doped carbon. Their hydrogen fuel cell has an anode (where hydrogen is oxidized) catalyst consisting of a solid nickel core surrounded by the carbon shell. When paired with a cobalt-manganese cathode (where oxygen is reduced), the resulting completely precious-metal-free hydrogen fuel cell outputs more than 200 milliwatts per square centimeter.
The presence of nickel oxide species on the surface of the nickel electrode slows the hydrogen oxidation reaction dramatically, Abruna said. The nitrogen-doped carbon coating serves as a protection layer and enhances the HOR kinetics, making the reaction quicker and much more efficient. In addition, the presence of the graphene coating on the nickel electrode prevents the formation of nickel oxides — resulting in electrodes with dramatically enhanced lifetimes. These electrodes are also much more tolerant to carbon monoxide, which rapidly poisons platinum. The study has been published in the journal Proceedings of the National Academy of Sciences.
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